The early steps in Tn10 genetic transposition are still unclear and not defined. A molecular spring has been proposed by Chalmer et al. (1998) to play an important role in Tn10 transposition and probably in many other biological systems as well. In addition to testing the molecular spring, this proposal is devoted to the effort to reveal the nature of event progression in the early steps of Tn10 transposition, such as how things come together and how the conformational changes in nucleoprotein complex(es) are coordinated. The molecular spring model will be tested vigorously with several DNA substrates presented. Intermediate nucleoprotein complex(es) will be trapped either by protein/protein or by protein/DNA cross-linking; protein and DNA chemistry will by employed to characterize and map the protein/DNA contacts. Biophysical means such as polarized fluorescence will be explored to detect 3D conformational changes occurring in the nucleoprotein complex(es).